Israel Underhill was born 10 September 1732 in Westchester County, New York, United Kingdom to Nathaniel Underhill (1690-1775) and Mary Hunt (1692-1775) .
Children
| Name | Birth | Death | Joined with |
| Marie Allaire Underhill (1766-1851) | 19 March 1766 Westchester County, New York, United States | 1 September 1851 Syracuse, New York, United States | Wynant Van Zandt (1767-1831) |
Siblings
| Name | Birth | Death | Joined with |
| Phoebe Underhill (1712-1775) | |||
| Sarah Underhill (1715-1761) | |||
| John Underhill (1718-1775) | |||
| Mary Underhill (1720-1788) | |||
| Frederick Underhill (1721-) | |||
| Nathaniel Underhill (1723-1784) | |||
| Bartholomew Underhill (1725-1786) | |||
| William Underhill (1727-1784) | 16 February 1727 Westchester County, New York, USA | 1784 Westchester County, New York, USA | Mary Dean (1728-1778) |
| Helena Underhill (1729-) | |||
| Glorianna Underhill (1731-1783) | |||
| Israel Underhill (1732-1806) | 10 September 1732 Westchester County, New York, United Kingdom | Williamsbridge, New York, United States | Abigail Lispenard (1739-1806) |
| Elizabeth Underhill (1735-1769) | |||